0
I have a disk image of a 500 GB that was created using the following:
# dd if=/dev/sda conv=sync,noerror bs=64K | gzip -c > backup.img.gz
There were certain errors (approximately 15-20 of them) stating the following, at a certain point above approximately 420 GB. The errors were interspersed by few GBs of data in between (so, for example, the first error was at 420 GB, the next at 430 GB, the next at 436 GB, and so on.)
dd: error reading '/dev/sda': Input/output error
Is it safe to restore this disk image?
No. What makes you think it would be? You will end up with a disk with unknown errors. – DavidPostill – 2016-07-28T17:59:57.123
if you do, restore it to other media, and copy the files you want back over manually. Also check the SMART status of your disk. Generally, DD should not encounter such an error on a healthy disk. – Frank Thomas – 2016-07-28T19:00:32.900